Measure and Value
Numbers Descriptive of Distance
Before the introduction of railways we scarcely possessed any standard by which an idea could be formed of the distances and movements of the planets by comparison with those which exist on the terrestrial globe. Thus, the mean distance of the moon from the earth is about 237,000 miles. A steam-carriage on a railway, proceeding uninterruptedly, at the rate of 25 miles an hour, would run 237,000 miles in 1 year, 4 weeks, and 2 days. This falls within the limits of our conception. We may imagine something analogous to this, supposing a carriage, or rather a succession of carriages, to be kept constantly at work for rather more than two years, and working 12 hours per day. But our powers of imagination fail us in estimating a distance equal to that of the earth from the sun, namely, ninety-five millions of miles.12 Our steam-carriage illustration is here no longer available, since it falls far beyond the boundaries of probability. Proceeding uninterruptedly at twenty-five miles an hour, it would require 433 years to move over a space equal to ninety-five millions of miles.—Dr. Lardner.